Helium

Physical and chemical properties

At room temperature, helium is an extremely light, colorless, odorless, and tasteless single atom gas. It is the most difficult substance to liquefy among all gases and cannot solidify at standard atmospheric pressure. When the temperature drops to 2.174K after liquefaction, it has special properties such as low surface tension, strong thermal conductivity, and extremely low viscosity. Low temperatures close to absolute zero can be achieved using liquid helium.

Chemical performance is stable, showing a deep yellow color during low voltage discharge. Generally, it does not generate compounds and can form He2+, HeH plasma and molecules when excited in low-voltage discharge tubes. In general, it is difficult to react with other substances, but under specific conditions, it can form compounds with certain metals. When the temperature drops to 2.18K, liquid helium undergoes a sudden change in properties, with extremely low viscosity, becoming a superfluid that can flow upwards along the container wall. Its thermal conductivity is 800 times that of copper, making it an excellent thermal conductor with exceptional thermal conductivity. Its specific heat capacity, surface tension, and compressibility are all abnormal. This abnormal liquid is called liquid helium II, while normal liquid helium is called liquid helium I.

[Main use]

1. Helium can be used as a propellant and booster for rocket liquid fuel, and is widely used in missiles, spacecraft, and supersonic aircraft.

2. Helium is used as a protective gas for smelting and welding, which is very important in shipbuilding, as well as the manufacturing of aircraft, spacecraft, rockets, and weapons.

3. Helium has excellent permeability and is used for cooling nuclear reactors, leak detection of pipelines, electronic and electrical devices in rockets and nuclear reactors.

4. Helium is a gas with ideal gas properties and is an ideal gas for vapor pressure thermometers at extremely low temperatures.

5. Helium has low mass density and weight density, and is not flammable. It can be used to fill light bulbs and neon tubes, and is also an ideal gas for balloons and airships.

6. Liquid helium can achieve a low temperature close to absolute (-273 ℃) for the manufacture of superconducting equipment.

7. Helium is a type of inert gas with lower solubility in the blood compared to nitrogen, making it less anesthetic. Therefore, helium is often mixed with oxygen as a breathing gas for divers.

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Packaging, storage and transportation

1. Packaging

Helium gas is generally packaged in high-pressure steel cylinders, which are gray in color and marked with green "helium". The filling of gaseous helium should be carried out in accordance with the national standard GB14194. The danger classification for packaging, storage and transportation in China is Class 2.2 non combustible gas, and the packaging mark for dangerous goods in China is 5.

2. Storage and transportation

Helium gas is non corrosive and can be stored using any universal material at room temperature. At low temperatures, copper, aluminum, and stainless steel materials are mainly used. Gas and liquid storage methods can be used. Gas cylinders should be stored in a cool and ventilated warehouse, with a temperature not exceeding 30 ℃, away from ignition and heat sources, and protected from direct sunlight. They should be stored separately from flammable and explosive materials.

Helium can be transported through pipelines or directly in transport canned containers, with a capacity of 1L~30m3. Liquid helium is used in industry for transportation and long-term storage in liquid helium transport tanks or fixed storage tanks, with a general volume of 100-500L.

Helium should be stored upright in a well ventilated, safe, and weather resistant place, with a storage temperature not exceeding 52 ℃. There should be no flammable materials in the storage area and they should be kept away from frequent entrances and emergency exits, and there should be no salt or other corrosive materials present. For unused gas cylinders, the valve cover and output valve should be properly sealed, and empty and full cylinders should be stored separately. Avoid excessive storage and prolonged storage time, and maintain good storage records.

【 Precautions 】

During the use of helium gas, the principle of first in, first out should be adopted. Suitable hand carts should be used to move the container, and the steel cylinder should not be pulled, rolled, or slid. Do not attempt to grab the lid of the cylinder to lift it; Ensure that the gas cylinder is in a fixed state throughout its use, and use a pressure reducing regulating valve or an independent control valve to safely release gas from the cylinder. Use a one-way valve to prevent backflow; Do not heat the gas cylinder to increase pressure and discharge. If the user has difficulties operating the cylinder valve, it should be stopped; Adjustable wrenches should be used to open valve covers that are too tight or rusty. Tools (such as wrenches, screwdrivers, pry bars, etc.) should not be inserted into the valve cover, otherwise it will damage the valve and cause leakage; Helium is compatible with all ordinary materials, and the design of pipelines and equipment must meet the pressure requirements.